Inbreeding, Incest, and the Incest Taboo:
The State of Knowledge at the Turn of the Century

Arthur P. Wolf + William H. Durham (editors)

That inbreeding produces offspring with lower fitness is now common
knowledge, as is the existence of a natural aversion to mating with
childhood associates, the "Westermarck Effect". The first was not
generally accepted until the second half of the 20th century, however,
and the second until its last few decades. The ten contributors to
Inbreeding, Incest, and the Incest Taboo explore this history, describe
the current state of biological, anthropological, and psychological
research in the area, and explore some of the continuing questions
and debates.

In his introduction, Arthur Wolf surveys the 20th century history of ideas
about incest. He looks back at a conference in 1957 and at Westermarck,
who was for so long a lone voice in the wilderness. Notable figures
with contrary positions included Sigmund Freud, Leslie White, Claude
Levi-Strauss, and Rodney Needham. Some claimed there was a natural
instinct for sexual relations with family, rather than an aversion;
some denied that an incest taboo existed at all; others claimed that it
was impossible for that taboo to be derived from a biological aversion.

Alan Bittles surveys rules about consanguineous marriages in different
religions and the laws in different Western countries and US states.
He also summarises the few attempts there have been to measure the actual
biological outcomes of incest.

Looking at the evidence from primates, Anne Pusey finds clear evidence for
avoidance of mating with maternal relatives, and a response to paternal
relatives that depends on social structure: "the patterns of inbreeding
avoidance are consistent with familiarity being the primary mechanism
of kin recognition".

Arthur Wolf presents results from his studies of "minor" marriages
in Taiwan, in which the wife was adopted by her husband's family as an
infant. Examination of their effects on fertility and divorce rates, and
the variation of these with the ages of wives and husbands at adoption,
suggests a slight modification of the Westermarck hypothesis:

"There is a remarkable absence of erotic feelings between people
who live together and play together before age ten. The absence
is particularly marked among couples brought together before age
three, and, for any given couple, largely depends on the age of
the younger partner when they first meet."

One commonly claimed counter-example to a universal incest taboo is
sibling marriages in Roman Egypt. Based on analysis of fragments of
census records, Walter Scheidel suggests that either large age differences
between spouses or upbringing by unrelated wet nurses may have prevented
an aversion resulting from childhood association.

Philosopher Neven Sesardic refutes the claim that there is a logical
problem with biological aversion to childhood associates producing social
sanctions against mating with relatives. He also explains why the case
studies that are evidence for the Westermarck Effect — situations where
there is avoidance of childhood associates even without social taboos —
are necessarily counterexamples to it being the cause of the incest taboo.

William Durham takes a contrary stance to some of the other contributors,
presenting ethnographic evidence that suggests incest taboos derive
from a rational understanding of the negative effects of inbreeding,
rather than or as well as from an innate aversion.

Hill Gates looks back at "anti-Freudian" anthropologist Bronislaw
Malinowski's work on incest among the Trobriand Islanders. She also
considers the idea that cultural evolution might in some cases run in
the opposite direction:

"Where conditions for ranking were auspicious, a family that
risked inverting taboo and ignoring aversion set in train
a snowballing status improvement for its descendants and
an evolutionary leap in social complexity for its society.
Somewhere in the history of all early states we might expect to
find royal brother-sister incest lurking."

Mark Erickson presents a clinical perspective. Incest disrupts familial
affiliation and bonding, which contributes to the trauma of incest and
helps to explain why victims of incest are more likely to commit incest
themselves.

In the final chapter, Larry Arnhart considers the incest taboo as an
illustration of how ethics can be rooted in natural human inclinations.
He places Westermarck in an intellectual tradition which goes back
to the Socratics, the medieval "natural right" tradition, Adam Smith,
and Charles Darwin, and forward to Edward O. Wilson.

Inbreeding, Incest, and the Incest Taboo is an excellent collection:
its pieces complement each other nicely, with little repetition, and fit
together to make an effective book. As a summary of current knowledge
on a topic at the heart of many theoretical debates, it will be helpful
to anthropologists; as an accessible presentation of a topic of popular
interest, it should command a much broader readership.